Abstract Seven medications have been approved for the treatment of tobacco addiction in the United States, five that are nicotine replacement and two are non-nicotine. Three of the NRT products (i.e. patch, gum, lozenge) are available as over-the-counter (OTC) products because clinical trials have shown that they are safe and effective without healthcare provider involvement. After multiple studies, including one of the largest smoking cessation trials (`EAGLES' study) ever conducted, the evidence is clear that varenicline has the greatest probability of helping the most smokers quit and results in adverse events that are no worse than current OTC NRT products. Given these data, the time has come to explore whether varenicline is safe and effective as an OTC medication. In addition, because earlier research found that .5mg twice a day (b.i.d.) varenicline is as effective as the currently FDA-approved 1.0mg b.i.d but with lower incidence of nausea and sleep disturbance, there is value in assessing whether the lower dose will work as well as the higher dose in an OTC environment. Thus, the primary goal of the proposed research is to test whether varenicline is a solid candidate for switching from prescription (Rx) to OTC, and whether a dose lower than that currently approved is as effective in an OTC environment. To understand the within- person mechanisms explaining how and when OTC varenicline might improve cessation outcomes, we also propose to assess experience with OTC varenicline via (a) ecological momentary assessment (EMA) and (b) interviews in a subset of participants.